SAN FRANCISCO — Mark Dantonio leapt from his chair when he got the news, a smile stretched across his face. And why wouldn’t it?

It’s been a largely dreary year for the Michigan State football coach, a year of injury and stalled offense and unmet expectation. So when star defensive tackle Raequan Williams strolled into his office recently to tell him he’d be back for his senior year, well, Dantonio’s reaction was understandable.

In a year when so many players with NFL talent opted to skip their team’s bowl game, here was Williams, opting to skip the draft. At a program like MSU, where the depth chart isn’t flush with future interior pros, a decision like that can change a season.

“Well, that's kind of a Happy New Year's deal,” said Dantonio. “He's an anchor guy, he's a guy that you can build your defense around. He's a dominant player for us and to have him return in a huge statement, not just for our defense, but for our program.”

Williams helped turn the Spartans’ defense into a force this fall. Yeah, it’s relative, especially as the bowl season has revealed a somewhat fraudulent Big Ten. Still, in the realm in which MSU operates, its defense often dominated.

Williams thinks it can get better, and that he can get better, too. This is partly why he returned.

“I don’t know what the scouts will see, but I feel like I need to get better in all aspects of the game,” he said. “I’m a better pass rusher than a sack and a half. I have to put that on film. I think I can do it.”

If he does, and if his fellow lineman, Kenny Willekes, returns for his senior year, the Spartans should have the best 1-2 defensive line combo in the league.

For all that has been written about Willekes’ rise and how he exemplifies Dantonio’s ability to pluck future stars from obscurity — the walk-on junior defensive end was named Big Ten lineman of the year — Williams’ ascension isn’t that dissimilar.

He arrived in East Lansing as a three- or four-star recruit, depending on the ranking service, but he wasn’t seen as a surefire All-American. He had quick feet and an expanding mid-section — he weighed 315 pounds — and hadn’t learned how to work, even though he liked to.

That attitude carried into the fall and landed him on the All-Big Ten’s first-team, a performance that kept MSU in games as the offense continued to scuffle.

Because the Spartans couldn’t score — they managed two touchdowns in their last three games — the defense didn’t quite get its due. In the last month of the season, you could argue there was no better unit in the league … including Michigan.

Williams and his teammates on that side of the ball slowed everyone, including Ohio State. With any offense at all, MSU wouldn’t be getting ready to play in the Redbox Bowl. They'd be getting ready for something better.

The Spartans’ defense took a hit last week when cornerback Justin Layne chose to skip the bowl game to prepare for the NFL draft. Layne, along with Josiah Scott, gave Dantonio his best pair of cornerbacks since 2013, when Trae Waynes and Darqueze Dennard patrolled the edges of the field.

It took five years for MSU to recreate that kind of cover skill on the outside. And while it took less time to reload the defensive front — before this season, the Spartans’ last dominant group up front played in 2015 — Williams' decision to return is a reminder of how difficult it can be to consistently compile the right pieces at a program like MSU.

His return gives Dantonio a foundational piece in the middle next year. Even without Layne, if everyone else returns, especially Willekes, the defense should have a chance to be formidable again.

MSU will not get back to where it thinks it belongs unless the offense finds its footing. That starts with quarterback Brian Lewerke. The Spartans will need better health luck on that side of the ball, too.

Dantonio referred to his program as a national brand this week. He said he and his staff still keep lofty goals.

And while it’s unlikely that he will oversee the kind of three-year run he had from 2013-2015, when he won two conference titles and a Rose Bowl, he should have enough pieces to compete in the Big Ten East next year and get to the level of the Kirk Cousins-led teams in 2010 and 2011.

This is another reason Williams wanted to return.

“I think we have a really good team coming back,” he said. “I feel like we underachieved a little bit for the talent we have on this team. We’ve got big things in the future we think.”

At the least, there is a future. Even if it doesn’t feel like it at the moment, as the offense slogs and the possibility that Oregon could put another whupping on the Big Ten.

Whatever happens in the bowl game, Dantonio has proven he can reset his program the next season. It’s easier to do when a force like Williams sticks around.

“When you start something you should be able to finish it,” he said. “I have a good relationship with Coach D, he’s like a father figure. Everybody around here has given me nothing but respect. And I talked to my guys, like (former MSU defensive end and current Oakland Raider) Shilique Calhoun, and everybody that I played with here who is in the NFL. They always say there is nothing like college. So I might as well enjoy it. Everything else can wait.”